1 in 5 Kids With Autistic Siblings Will Also Be Autistic New study shows higher risk than previously thought By Evann Gastaldo, Newser Staff Posted Aug 15, 2011 8:48 AM CDT 2 comments Comments Kathleen Lanese of Kings Park, NY, poses with her two autistic sons Brendan, 14, right and Kevin, 10 at her sister-in-law's home on Thursday, Aug. 11, 2011, in Oyster Bay, NY. (AP Photo/Kathy Kmonicek) (Newser) – Researchers were "surprised and taken aback" by the results of a new study, which suggest about 19% of children with an autistic older sibling will also develop the disorder—a much higher rate than the 3% to 14% previous studies have shown. Of the 664 infants studied by researchers, all of whom had at least one older sibling with the disorder, 132 were diagnosed with autism by age 3. Studies done in the past have been smaller or more localized and less diverse; this study was done in 12 US and Canadian sites. The risk was higher for boys, for whom autism is more common, with 26% developing the disorder compared to 9% of girls. And for infants with at least two older autistic siblings, the risk shot up to 32%, the AP reports. The lead author says the study provides an updated answer to the common question raised by parents of autistic children: "How likely am I to have another child" with the disorder? But she warns that the prevalence rate is only an average, and other risk factors could influence each individual family's risk.